Structured heavy duty liquids must be able to suspend particles such that these particles do not phase separate (i.e., settle out of solution) and yet they must not be so thick as to effect the pourability of the liquid compositions.
The dual attribute of suspending power and easy pourability in structured or duotropic liquids currently in the art is accomplished by adding sufficient surfactant and/or electrolyte such that the surfactant forms a disperse, lamellar phase. The prior art liquid compositions are capable of suspending only small (&lt;25 .mu.m) particles such as, for example, zeolites.
Duotropic liquids such as those described above are taught for example in U.S. Pat. No. 5,147,576 to Montague et al., WO 91/09107 to Buytenhek et al., EP 0,160,342 A2 to Humphreys et al., EP 0,564,250 A2 to Coope et al. and WO 91/08281 to Foster et al.
The use of solids of the morphology described in the present invention in structured heavy duty liquids is taught in EP 0,086,614 A1 to Akred et al. However, there are significant differences between the solids and the structured liquid composition mentioned in the above specification and those taught in the current specification. These are as follows:
i) the dimension of the solids used by Akred et al. is not critical while that required to structure structured liquids of the present specification is 1 to 25 microns; PA1 ii) the solids of Akred et al. have to form a network (i.e., solids are coordinated with each other rather than being independent) in the structured liquid while those used in the current specification do not form network as evidenced from rheological measurements; structuring by network formation is undesirable since it takes a considerable amount of time to rebuild the network when the structurant is disturbed (for example, during use of the product) and during this rebuilding the solids can settle out time; furthermore, it is extremely difficult to reproduce the network formation which will reflect in inconsistency in quality of the product formed; and PA1 iii) the lamellar droplets of the structured liquid used in the current specification are stabilized using a decoupling polymer, while no stabilizing agent is used in Akred et al. Use of decoupling polymer allows incorporation of much higher levels of surfactants into the detergent formulation. Structured liquids containing decoupling polymers are described in Montague et al. (U.S. Pat. No. 5,147,576) hereby incorporated by reference into the subject application. PA1 (2) a solid particle, added directly or formed in situ, wherein at least one side of the particle (length or width) is from about 3 to 20 microns in size; PA1 (2) 0.1 to 5% by weight of a deflocculating polymer; and PA1 (3) 1% to 25%, preferably 3% to 15% by wt. of a solid particle, added directly or formed in situ, wherein at least one side of the solid has a length or width of from 3 to 20 microns. Preferably, the width of the particle is less than about 1 micron and the length (being no less than 3 microns) is at least 3 times the width, preferably 5 times the width. The larger the length is relative to the width (i.e., the more "needle-like" the solid), the greater is the suspending power which was observed. PA1 (1) unsaturated, preferably mono-unsaturated, C.sub.1-6 acids, ethers, alcohols, aldehydes, ketones or esters such as monomers of acrylic acid, methacrylic acid, maleic acid, vinyl-methyl ether, vinyl sulphonate or vinylalcohol obtained by hydrolysis of vinyl acetate, acrolein; PA1 (2) cyclic units, unsaturated or comprising other groups capable of forming inter-monomer linkages, such as saccharides and glucosides, alkoxy units and maleic anhydride; PA1 (3) glycerol or other saturated polyalcohols.
While lamellar structured compositions possess shear thinning characteristics to provide suspending power for small particles (less than 25 .mu.m) and maintain pourability, they do not possess sufficient shear thinning property to provide adequate suspending power for large particles (i.e., 200 to 1000 microns) such as, for example, encapsulates of bleach catalysts and enzymes,